1. The atomic number = 7, atomic mass = 14, number of electrons = 7.
2. Isotopes are atoms of the same element with a different number of neutrons (and therefore a different weight). Many isotopes are unstable and tend to decay at a constant rate, and are therefore useful in scientific dating techniques. Since the number of electrons is the same, different isotopes of a single element have the same chemical properties.
3. It will contain 8 milligrams and 4 milligrams, respectively. It will take 6,660 years.
4. A cation is a positively charged ion. An anion is a negatively charged ion.
5. An electron closer to the nucleus of an atom has more potential energy. During the transfer of electrons between atoms in a chemical reaction, the energy of position of the electron is maintained. Loss of an electron is oxidation, gaining an electron is reduction.
6. The octet rule states that atoms completely fill outer energy levels. Behavior of atoms both singly and during chemical reactions is strongly influenced by this phenomenon, which accounts for the bonding behavior of most atoms.
7. An ionic bond is formed when electrons from one atom are donated to another; an example is NaCl (sodium chloride). A covalent bond is formed when electron orbitals of two atoms overlap such that electrons are shared between the two atoms; an example is H2O (water).
8. Oxygen and hydrogen atoms contribute to the formation of hydrogen bonds. Slightly electronegative oxygen regions of molecules (usually water) are attracted to the slightly electropositive hydrogen atoms, polarizing the molecules in a specific way. Hydrogen bonds are very weak, especially in comparison to covalent bonds, but several hydrogen bonds acting in concert are strong enough to stabilize large molecules or provide surface tension in water. Water has a high specific heat because a lot of thermal energy is required to disrupt the hydrogen bonding in water to raise its temperature.
9. Hydrophobic molecules are nonpolar molecules that will not form hydrogen bonds readily with water, so consequently, will self-associate. Hydrophilic molecules do form hydrogen bonds with water.
10. pH is equal to -log[H+]. A solution with a hydrogen ion concentration of 10-3 mole/liter would have a pH of 3 and would be acidic. A solution with a hydrogen ion concentration of 10-9 mole/liter would have a pH of 9 and would be basic.
11. As hydrogen ions increase, more bicarbonate ion is released, increasing pH. If hydrogen ion concentration in the blood increases, carbonic acid in the blood dissociates, liberating hydrogen ions into the blood and decreasing pH. This is an example of a homeostatic mechanism that helps maintain constant blood pH, critical for survival in most organisms. Since pH is a logarithmic scale, even a slight deviation in blood pH represents a big change.